Line A. Kyhn
The mammal monitoring programme was performed by Niels Martin Schmidt 19
May – 15 June, Line A. Kyhn 16 June – 29 August and Toke Høye 28 June – 26 July. Additionally, mammals were systematical- ly recorded by Hans Meltofte 31 May – 15 June and Jannik Hansen 31 May – 1 Au- gust. The station personnel and visiting re- searchers supplied casual observations during the entire field season.
The census area for collared lemmings was surveyed for winter nests during 1 July – 25 August. During the entire field season musk oxen were censused in the evening (between 20 and 23 hrs) from a fixed elevated point at the research station, provided that there was sufficient visibili- ty. In addition seals hauled out on the fjord ice and arctic hares on the east-facing slope of the Zackenberg Mountain were censused systematically, seals until the ice became too fragmented on 3 July. Every week between 4 July and 29 August, the 40 km2musk ox study area was censused in-
cluding records of sex and age classes of musk oxen. The yearly 170 km line tran- sects Zackenberg – Store Sødal and Zack- enberg – Daneborg was performed 16-18 and 20 July, respectively, by Toke Høye and Line A. Kyhn.
The 14 known fox dens within the 50 km2fox study area and one just across the
eastern border (Kuhnelv) were checked regularly for occupation and breeding, and the only den known between Dane- borg and Kuhn River was checked on 21 and 29 May and again on 20 July.
The collared lemming population
Following the ‘missed’ collared lemming Dicrostonyx groenlandicus winter peak of 01/02 and the low density of 02/03, a con- tinued growth from the medium peak last winter was expected for the winter 04/05 as a result of an apparently absent stoat population in winter 03/04 (Tables 3.34 and 3.35 and Fig. 3.6). However, the growth did not continue and the 232 win- ter nests of 04/05 were medium low for Zackenberg.
The fox population experienced a peak in summer 2004 with at least 18 pups pro- duced (Rasch and Caning 2005). This im- pact can have reduced the lemming popu- lation even before they settled under the snow, as lemmings are most exposed in their summer habitat and when moving between summer and winter habitats (Schmidt et al. 2002, Kyhn 2004). As the snow accumulated very late in autumn
2004 (data from the meteorological station and section 2.2), the summer predation may have lasted much longer than in nor- mal years, which might have had a pro- nounced effect on the lemming popula- tion. However, with no predation by stoats the lemming population have been re- markably low for two consecutive winters. The stoat situation at Karup Elv, approxi- mately 220 km south of Zackenberg, was much different, as they had record high numbers of stoat predated lemming win- ter nests despite a missed lemming peak in the winter of 03/04 (Fig. 3.6).
Of the 232 new nests found at Zacken- berg in 2005, 190 were build in the vegeta- tion, which is assumed to indicate that they were build in the beginning of the season, and 24% of these were breeding nests. Also 24% of the 41 nests build on top of the vegetation, i.e. in the snow pack, were breeding nests.
Again this year, not a single of the ex- amined winter nests was found to have been depredated by stoats, and no stoat scats were found during the systematic study (Table 3.36). After the lemming low in 95/96 the stoat population needed two years to recover (Fig. 3.6). The lemming population has not experienced a full peak since 97/98 and this might explain the ab- sence of stoat predated winter nests in
03/04 and 04/05. For the seasons to come the lemming population should increase dramatically in response to the relaxed stoat predation, if reacting as most de- scribed lemming populations.
This year 154 old winter nests were found. This is surprising, since the area has been monitored systematically since 1995. The most likely reason for this is that the observers this year were new to the sampling procedure and therefore very cautious and vigilant during the sampling. However, inexperience might also explain for some mis-categorization of nests, but most of the old nests recorded were very old and not just worn from the winter.
Winter nests Animals seen
category 1 category 2 1995 285 821 – 1996 161 263 0 1997 342 109 1 1998 711 109 43 1999 305 57 9 2000 184 70 1 2001 318 22 11 2002 311 29 4 2003 96 31 1 2004 431 24 23 2005 232 154 1
Distance Winter nests
km No. No./km Store Sødal 1996 150 2 0.01 1997 300 11 0.07 1998 150 21 0.14 1999 130 3 0.02 2000 130 1 0.01 2001 130 13 0.10 2002 130 9 0.07 2003 130 12 0.09 2004 108 2 0.02 2005 130 2 0.02 Daneborg - Zackenberg 1997 50 22 0.44 1998 50 17 0.34 1999 40 1 0.03 2000 40 0 0,00 2001 40 24 0.60 2002 40 5 0.13 2003 40 1 0.03 2004 40 16 0.40 2005 40 22 0.55 0 2 4 6 8 10 12 14 87/8888/8989/90 90/9191/92 92/9393/9494/95 95/9696/97 97/9898/9999/00 00/0101/02 02/0303/0404/05 Winters Nest depredated/km 2 0 50 100 150 200 250 300 350 400
Lemming winter nest/km
2
Karupelv: stoat Zackenberg: Stoat Karupelv: Lemming Zackenberg: Lemming Table 3.34. Annual numbers of lemming winter nests
recorded within the 2.05 km2census area in Zacken-
bergdalen 1995-2005 together with the numbers of animals encountered by one person (2005: N.M. Schmidt 1-15 June and J. Hansen 16 June-31 July) with
comparable effort each year within the 19 km2bird
census area during June-July. Numbers from previous years have been corrected following a critical review of the data. Category 1 denotes nests from the previous winter, category 2 nests from earlier winters that were not recorded previously.
Table 3.35. Lemming winter nests recorded along the 170 km tran- sects Zackenberg – Store Sødal and Daneborg – Zackenberg 1996-2005. Nests were recorded within 3 m on each side of the two observers.
Fig. 3.6. Lemming winter nest density (right axis) and stoat predation on lemming nests (left axis) within the census area in Zackenbergdalen (2.05
km2) and at Karup Elv,
Traill Ø (10km2) 220 km
south of Zackenberg (kindly provided by Benoit Sittler). Data include nests built from October until May. Nests and nest pre- dation by stoat are given
Musk ox population biology
The pattern of musk ox Ovibos moschatus occurrence in Zackenbergdalen as record- ed daily during counts from the research station closely matched the patterns ob- served in 2001, 2002 and 2004 (Fig. 4.6 in Caning and Rasch 2003, fig. 4.4 in Rasch
and Caning 2003 and fig.3.5 in Rasch and Caning 2005, respectively) with high num- bers in May-June, lower in July and in- creasing again to the highest counts in Au- gust. This pattern with many oxen in June correlates well with the early snowmelt in the beginning of June, as for last year. In 2005 the number of musk oxen per obser- vation was extremely high and the record so far both within the 40 km2census area
(Table 3.37) and in the entire visible area of 135 km2(Figs 3.7 and 3.8). There were 131
oxen per observation in 2005 and 114 in 2004 for the entire area visible during counts from the station. Until then, the record was 82 in 1995, whereas the lowest number recorded was 37 in 1999. This is quite a large variation in relation to the total musk ox population of Wollaston Forland and A.P. Olsen Land, which is estimated to encompass some 500-800 ani- mals (Boertmann and Forchhammer 1992, Rasch and Canning 2003).
Looking at records of piles of faeces counted along the line transects in July, the number of winter faeces usually cor- responds to the number of musk oxen counted in Zackenbergdalen during sum- mer, but for the last two years these num- bers have been decreasing despite that the numbers of musk oxen in Zackenberg- dalen have increased drastically (Table 3.38). This implies that the musk oxen must have spent the winter elsewhere
than in Store Sødal and along the coast to- wards Daneborg.
The two line transects Zackenberg –
Skua Owl Fox Stoat
casts casts scats scats
1997 44 0 10 1 1998 69 9 46 3 1999 31 3 22 6 2000 33 2 31 0 2001 39 2 38 3 2002 32 6 67 16 2003 16 0 20 1 2004 27 0 16 3 2005 7 6 24 0 Table 3.36. Numbers of casts and scats from predators collected from 29 permanent sites within
the 2.05 km2lemming
census area in Zacken- bergdalen. The samples represent the period from mid/late August the pre- vious year to August in the year denoted.
May June July August Total
1996 445 445 2412 3302 1997 290 1086 1432 2807 1998 522 635 1121 2278 1999 361 392 1292 2045 2000 478 898 1543 2919 2001 923 1257 1689 3868 2002 418 448 1819 2684 2003 287 638 2247 3172 2004 1311 786 3285 5381 2005 1064 2090 1353 3449 6891
Table 3.37. Total numbers of ‘musk ox days’ per month, calculated as accumulated numbers of musk oxen recorded per day during the respective months within
the 40 km2census area in Zackenbergdalen based on
the daily counts from a fixed elevated point at the research station 1996-2005. NOTE: Data from 2004 have been recalculated. May is not included in the total.
0 50 100 150 200 250
24-maj 13-jun 03-jul 23-jul 12-aug 01-sep
No. of musk oxen
0 20 40 60 80 100 120 140 160 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
entire visible area
census area
Fig. 3.7. Numbers of musk oxen (one week running means) recorded from a fixed ele- vated point at the research station in 2004 (thin line) and 2005 (medium line) along with average from all years (heavy line).
Fig. 3.8. Annual average numbers of musk oxen/observation counted from a fixed ele-
vated point at the research station 1996-2005 in the 40 km2census area and in the entire
Store Sødal and Zackenberg – Daneborg were walked on 16-18 and 20 July, respec- tively. The associated weekly musk ox cen- sus was walked on 15 July. A total of 130 animals were aged and sexed out of a total 154 animals observed. The main part of these was encountered on the Zackenberg – Daneborg transect just east of the border of the musk ox census area, i.e. on the slopes of Cardiocera Mountain. 26% of the aged animals were calves and 25% were reproductively active females (+4 years). This gives a mother/calf ratio of app. 1:1, which is double the expected ratio, since a cow only gives birth every second year ac- cording to the literature, and previous years with an observed mean of 2.2 cows per calf. In 2004 there were two calves per cow, and the high ratio again this year
likely reflects that the last couple of years have provided good conditions for the musk oxen, since so many cows have been able to divert energy for calf production two years in a row. Secondly, since calves are born April to June the high number of calves also reflects the warm spring and early snowmelt providing optimal condi- tions for new born calves.
Since 1996, the ratio between males and females in the different age classes has been approximately equal until the class of 3yrs (except in 2005) (Table 3.39). For 3yrs and 4+ yrs there are more females (means of 8.4 and 40.9, respectively for the two classes) than males (means of 4.3 and 30.6, respectively). Looking at the record of car- casses, 4+ males are overrepresented mak- ing up 49% of the total sample as opposed
Store Sødal Zackenberg- Daneborg- Snow cover (%)
dalen Zackenberg Zackenberg 10 June
Musk oxen/km2 1996 0.37 0.33 – 77 1997 0.39 1.58 0.13 81 1998 0.62 1.18 0.86 80 1999 0.78 1.20 0.70 92 2000 0.25 2.10 0.22 54 2001 0.31 3.38 0.92 82 2002 0.69 1.68 0.30 77 2003 0.26 1.70 0.22 83 2004 0.28 0.10 0.73 49 2005 0.38 1.03 2.22 28 Faeces piles/km 1997 winter/summer 1.38 / 0.30 – 6.13 / 1.03 81 1998 winter/summer 1.49 / 0.35 – 1.25 / 0.23 80 1999 winter/summer 7.71 / 2.00 – 4.58 / 3.08 92 2000 winter/summer 2.87 / 0.46 – 1.13 / 0.28 54 2001 winter/summer 6.82 / 1.36 – 2.63 / 0.45 82 2002 winter/summer 5.12 / 1.88 – 4.73 / 0.60 77 2003 winter/summer 9.34 / 3.00 – 3.70 / 0.68 83 2004 winter/summer 2.33 / 4.13 – 4.03 / 3.45 49 2005 winter/summer 2.32 / 1.80 – 0.73 / 2.15 28 Calf F1 M1 F2 M2 F3 M3 F4+ M4+ Total 1997 13 5 6 13 14 8 2 32 10 103 1998 11 6 7 8 8 8 7 44 23 122 1999 24 0 0 9 8 13 7 58 52 171 2000 25 6 7 4 1 7 6 47 44 147 2001 27 10 7 6 7 6 1 58 38 160 2002 21 10 9 12 10 10 4 57 40 173 2003 18 6 7 3 5 3 4 34 29 109 2004 11 4 2 2 8 7 6 19 59 2005 34 5 10 5 10 13 1 32 20 154
Table 3.38. Musk ox den-
sities (animals/km2) in
Store Sødal (92 km2 in
1996-1998 and 125 km2
in 1999 and onwards), the census area in Zacken-
bergdalen (40 km2) and in
the coastal region between Daneborg and
Zackenberg (37 km2) in
mid/late July 1996-2005. Also densities of faeces piles (no. of piles/km walked) in Store Sødal (150 km in 1997-1998, 130 km in 1999-2003, 2005 and 54 km in 2004) and from Daneborg to Zackenberg (40 km) are given. Densities from ear- lier years have been recal- culated.
Table 3.39. Sex and age distribution (actual num- bers) of musk oxen based on total counts along the two line transects and the related total census in Zackenbergdalen 1997- 2005. All counts were made within 16-30 July and covered an area of
approximately 200 km2.
Possible double counts have been omitted. Note, 24 of the musk oxen encountered in 2005 were not aged and sexed.
to 22% females in the same age class (Table 3.40). The sex ratio is close to even for the younger age classes. These shifted sex ra- tios might rely on differences in natural causes of death, difficulties in separating 3 yrs males from 4+ yrs females or that young bulls may form bachelor groups with a different activity pattern and area use.
Arctic fox dens
2005 was not the best year for foxes Alopex lagopus as no pups or intense den use indi- cating offspring were observed over the season. However, the number of adult foxes observed was the second highest recorded (Table 3.41), which may indicate that many of the minimum of 18 pups pro- duced in 2004 actually made it through the winter. This is in accordance with the number of musk ox carcasses observed (Table 3.40), but not with the very low number of lemming winter nests found (Table 3.34), which equalled the situation in 1996. Intense competition for food over winter and spring among the foxes might thus have hindered the allocation of ener- gy for reproduction and hence a new gen- eration this year.
Six dens seemed occupied over the sum- mer (nos 1, 2, 3, 4, 10 and 12), and three were occasionally in use (nos 5, 7 and 9) (Table 3.42).
Two new dens were found this year, each consisting of one entrance and si-
Snow cover Thaw Total 4+ yrs 3 yrs 2 yrs 1 yr Calf
10 June (%) hours carcasses F / M F / M F / M F / M
1994-1995 76 ? 2 0 / 1 1 1995-1996 77 47 13 7 / 1 0 / 1 0 / 2 1 / 1 1996-1997 81 9 5 0 / 2 1 / 0 1 / 0 1 1997-1998 80 83 2 0 / 2 1998-1999 92 32 1 0 / 1 1999-2000 54 35 8 0 / 6 1 / 0 1 2000-2001 82 13 4 0 / 4 2001-2002 77 88 5 1 / 2 1 / 0 1 2002-2003 83 178 3 0 / 2 1 2003-2004 49 50 2 1 / 1 2004-2005 28 39 6 2 / 3 1
Table 3.40. Fresh musk ox carcasses found during the field seasons of 1995- 2005. F = female, M = male. ‘Thaw hours’ are numbers of hours during October-April with posi- tive temperatures, which may have caused ice crust on the snow. Note: Two of the carcasses found in 2005 died in July.
Total Total No.
no.of no.colour of fox
records phase carcasses
1996 34 31W + 3D 1997 22 17W + 5D 1W + 1D 1998 24 21W + 3D 1W 1999 19 18W + 1D 2W 2000 28 28W 2W 2001 55 54W +1D 1W 2002 23 23W 0 2003 50 50W 0 2004 90 90W 0 2005 58 58W 0
No. of No. of No. of Total no. No of Lemming
known dens dens in use breed. dens of pups muskox winter
inside/outside inside/outside inside/outside recorded carcasses population
1995 2/0 0/0 0/0 0 2 decrease 1996 5/0 4/0 2/0 5W + 4D 13 low 1997 5/0 1/0 0/0 0 5 increase 1998 5/0 2/0 1/0 8W 2 peak 1999 7/0 3/0 0/0 0 1 decrease 2000 8/0 4/0 3/0 7W 8 low 2001 10/2 6/1 3/1 12W + 1D 4 increase 2002 10/2 5/1 0-1/0 0 4 intermediate 2003 11/2 8/1 3/0 17W 2 low 2004 12/2 12/2 4/1 18+W 2 increase 2005 14/2 6/0 0/0 0 6 low Table 3.42. Numbers of known fox dens in use, numbers with pups and the total number of pups recorded at their maternal
dens within the 50 km2
fox census area in Zacken- bergdalen. ‘W’ and ‘D’ denote white and dark colour phase, respectively. Dens in use are defined as dens showing signs of use over the entire summer season.
Table 3.41. “Total number of records“ gives the number of records of all adult and those of juvenile foxes encountered in the field away from their maternal den during June- August 1996-2005. Note: 20 white fox records were made in May 2005.
tuated under a large stone near den 4 and 12, respectively.
For all dens, the total number of en- trances was counted in order to allow for analysis of development over the coming years. Especially den 1 seems to be going through some restructuring, as the roof is falling down in some places and new en- trances are formed. Generally dens nos 1, 2, 3, 4, 10 and 12 appear to be very old, as they hold many entrances.
Arctic hare
This year an average of 13 hares Lepus arcticus per observation was recorded during the daily counts covering the east- facing slopes of Zackenberg. Observations were made from a fixed elevated point at the research station (calculated as number of hares per observation day) in conjunc- tion with the daily counts of musk oxen. Totally, a factor 10 more hares were ob- served in 2005 than previous years (Table 3.43). Mech (2000) found that an early on- set of winter had adverse effect on the re- productive success of arctic hares by short- ening their summer replenishment period. Oppositely, a delayed onset of winter with late snow fall in the autumn of 2004 (the meteorological station and section 2.2) and early snowmelt of 2005 are the likely fac- tors explaining the increase in number of hares observed. A delayed onset of snow may be beneficial to arctic hares, as contin- ued access to forage during autumn likely increases hare fitness, preparing them bet- ter for the coming winter.
The number of arctic hares observed at other sites than Zackenberg Mountain was correspondingly high this season. How- ever, 60 of these 150 hares were observed on the slopes of Aucella during the daily musk ox census.
The total numbers of arctic hares ob- served per day increased during the sea- son with largest numbers occurring from mid July until late August (Fig. 3.9), and there was a tendency for the group size to increase correspondingly over summer. This probably reflects that the leverets be- come more active and that female hares expand their home ranges in association with a more relaxed behaviour when nursing of leverets is over in July (Hearn et al. 1987). In general, hares seem more ac- tive at night time, when they gather in larger groups and are more often observed in the lowlands than during the day,
where they are most often observed be- tween boulders on mountain hill sites (personal observation during three sea- sons).
Other observations
Arctic wolf Canis lupus
Three times during the season fresh tracks were observed in Zackenbergdalen. Stoat Mustela erminea
Stoats were observed at two occasions in Zackenbergdalen, one inside the station area, the other at the slopes of Aucella- bjerg. No scats were found during the systematic scat and casts collection (Table 3.36), which is in accordance with the ob- servation that no lemming winter nests had been depredated by stoats during the winter 04/05 (see the lemming population chapter for discussion).
Seals Phoca spp.
Seals hauled out on the ice of Young Sund are primarily ringed seals Phoca hispida, but also bearded seals Erignatus barbatus are present in the area, just as hooded seals Cystophora cristata and harp seals Phoca groenlandica can occur. The species can not be identified during the daily cen- suses from the research station. This year seals were censused until 3 July when the
Sum Average ± SD Range Counts Others
2000 57 1.74 ± 2.9 0-11 16 67 2001 52 0.84 ± 1.52 0-6 22 72 2002 17 0.27 ± 0.73 0-4 16 19 2003 94 1.45 ± 2.82 0-13 20 42 2004 56 0.89 ± 1.7 0-3 23 135 2005 607 6.08 ± 8.59 0-30 48 150 Table 3.43 Numbers of arctic hares counted daily from a fixed elevated point at the research sta- tion during June-August 2000-2005. Average, SD and range are based on sum pr. observation day. “Others“ are hares observed incidentally in the field. Only counts per- formed with good visibility are included. Note: Data has been recalculated for all years. 0 5 10 15 20 25 30 35 20- May 27- May 03- Jun 10- Jun 17- Jun 24- Jun 01- Jul 08- Jul 15- Jul 22- Jul 29- jul 05- Aug 12- Aug 19- Aug 26- Aug
No. of hares per observatio
n
Fig. 3.9 Total number of arctic hares observed from a fixed elevated point at the research station during daily census in 2005.
ice became too fragmented. There was an average of 13 seals per count, which is low compared to a mean of 24 for all years (Table 3.44).
On a visit to Sandøen on 18 August six